It is often desirable to accumulate a sample of a fluid, such as natural gas, in cylinders for later analysis. Several sample cylinders have been invented over time, such as those described in U.S. Pat. Nos. 4,922,764 and 4,459,865 both having common inventorship herewith. A problem exists with these and other previous designs when it is necessary to purge the entire contents from the cylinder to avoid even minute contamination of subsequent samples.
Furthermore, sample cylinders typically have end caps that fit into the cylinder bodies. To prevent leakage of the sample, o-rings are placed between the sample cylinder and the end cap. O-rings leave behind gaps between the o-ring groove of the end cap and the o-ring itself. These gaps can hold trace amounts of a sample, which can slightly contaminate subsequent samples.
It is therefore an object of the present invention to provide a sample cylinder with the ability to purge the entire contents thereof when desired by the user.
It is further an object of the present invention to provide a sample cylinder without gaps between the cylinder body and the end cap.
Other objects of the invention will become apparent from the specification described herein below.